The invention relates to a construction for a heddle frame in which heddles holding warp yarns are reciprocated up and down in a shedding operation during weaving on a loom. With the advent of high speed shuttleless looms the problem of reducing wear and noise in the parts of rapidly moving sub-assemblies of the loom, such as the heddle frame, is one to which considerable attention has to be given. In the case of the heddle frame, the metal heddles are typically fastened to a metal heddle rod by means of slots in which the heddle rod is received and between which there is considerable wear and noise due to the space and play therebetween as a tight fit is not possible. Moreover, to achieve high speed performance in the loom, the moving parts must weigh as little as possible and in the case of a heddle rod exhibit as high a bending resistance as possible.
In the prior art, it has been proposed to construct a heddle rod from a lightweight fiber reinforced plastic (U.S. Pat. No. 3,754,577) and to apply a metal or ceramic by plating to those regions of the heddle rod subjected to wear (British Pat. No. 1,308,326). In lieu of plating, it has been suggested to snap or glue a sheetmetal covering over the heddle rod to provide higher bending resistance (German Pat. No. 2,933,442).
In an almost opposite approach to the same problem, the use of a light-weight metal rod has been proposed which carries a synthetic plastic material resistant to impact, wear, and abrasion at the locations of impact which can be replaced and renewed (U.S. Pat. No. 4,106,530).
However, the above attempts to providing parts which operate with reduced wear and noise have not been entirely satisfactory. Many of the proposed heddle rod constructions require special plastic to metal connections or special heddle frames and are not readily usable with conventional heddle frames. The use of metal platings and coverings presents problems in the retention of the metal on the heddle rod under the rigorous forces encountered during cyclid reciprocation. Moreover, the metal platings and coverings utilized heretofore have not satisfactorily afforded the light-weight structures resistance to bending as is encountered during high-speed vertical reciprocation.
Accordingly, an important object of the present invention is to provide a heddle rod of light-weight construction having low wear and noise characteristics.
Another important object of the present invention is to provide a heddle rod particularly suitable for high-speed loom operation.
Another important object of the present invention is to provide a light-weight heddle rod which is readily usable with conventional heddle frames and may be reliably attached in accordance with known techniques.
Yet another important object of the present invention is to provide a light-weight heddle rod having a laminated construction of metal and non-metallic materials of different elasticity.
Still another important object of the present invention is to provide a heddle rod constructed having two outer metal layers and a core of dissimilar metal and/or a non-metallic material bonded therebetween providing a high modulus of elasticity in the vertical direction.